


Seaward on the Waves

by KandiSheek



Series: Kinktober 2020 [21]
Category: Iron Man (Movies), Marvel Cinematic Universe
Genre: Alternate Universe - Merpeople, Animal Instincts, Drowning, Frottage, Getting to Know Each Other, Graphic Description, Hopeful Ending, Interspecies Sex, Iron Man 1, Kinktober, Kinktober 2020, Language Barrier, M/M, Miscommunication, Misunderstandings, Near Death Experiences, Rutting, Steve is a merman, Tony is Ironman, Underwater Sex, Vibrators, Weird Biology, just not in the way you think
Language: English
Status: Completed
Published: 2020-11-17
Updated: 2020-11-17
Packaged: 2021-03-10 05:54:41
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,050
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27608612
Author URL: https://archiveofourown.org/users/KandiSheek/pseuds/KandiSheek
Summary: Tony gets saved from drowning by a merman which, up until that point, he didn't even know existed. He is especially surprised when that merman has no compulsions about being the first of his species to ever have sex with a human. In fact, the mer seems pretty excited about it.Tony knows an opportunity when he sees one.
Relationships: Steve Rogers/Tony Stark
Series: Kinktober 2020 [21]
Series URL: https://archiveofourown.org/series/1948957
Comments: 55
Kudos: 228





	Seaward on the Waves

**Author's Note:**

> Okay, so, hear me out. When I read the prompt 'Vibrator' I thought, well, I've done that a million times, how can I make this interesting? I was watching some sort of deep-sea fish documentary around that time and thus my brain derailed into weird realms of porn that I've never ventured into before. Please don't judge me.
> 
> Anyway, I'm excited (and a little scared) to see if this is the fic that breaks the camel's back. I've written some weird porn in my day but I daresay this one takes the cake. Thanks for reading and I hope you enjoy it!
> 
> Kinktober Prompt 21: Vibrator

Tony really should've thought about the ice.

“JARVIS?” he asked, his voice taking a sharp turn towards panic when his thrusters failed. “JARVIS, can you hear me?”

His heart lurched when he plummeted towards the ocean rushing up to meet him, fumbling for the latch on his side. “Come on, we gotta break the ice! JARVIS!”

The HUD stayed black and Tony wanted to throw up as he spun through the air uncontrollably, all his systems down and – oh fuck, he was going to die –

“Systems online.”

The blue light of the HUD flickered and Tony could've cried when his repulsors powered up with a loud whine, aiming them at the ground to stop his fall. He screamed, pulling himself out of free fall with a relieved laugh –

And crashed in the water.

Something sparked in the circuitry before it shut down, a safety measure to prevent it from electrocuting him, and the HUD went black.

“No no no no no –“ Tony desperately jabbed at the eject functions before he fumbled for the latches, staring up at the reflection of the moon that was rapidly fading as he sunk into the ocean. Water started leaking in through cracks in the suit, running down his body like ice cold fingers clawing at his ribs. “Fuck, JARVIS! Call – fuck, _help!”_

He finally got his right leg plate detached, hissing as the freezing water rushed in. Fuck, he had to get the rest of it off before –

He grunted when something hit him in the back, flattening him against the – oh fuck, he'd touched ground already, how deep was the ocean here?

 _96 feet in New York harbor,_ Tony thought randomly as he struggled to detach the other leg, his right one already going numb. He had no idea where he'd landed. Somewhere in the ocean, god, he didn't even know if he could make it to the surface –

Tears stung his eyes as the water steadily rose around him, already reaching up to his chest. He could see tiny bubbles in the air above him as his precious oxygen escaped through the armor, fuck, he needed that, he needed to get out –

The other leg detached and Tony fumbled for purchase on the chest plate. Maybe he could keep the helmet on – it could give him a few precious seconds, he could probably make it if he –

Something jostled him and Tony gasped when it tilted the armor, enough to allow air to rush out through his open leg pieces, slowly but surely filling the helmet with water.

“N–“ was as far as he got before his head was fully submerged and he closed his mouth with a rush of panic – fuck, he hadn't even breathed in, he was so dead –

Something tugged on him and then suddenly the entire armor lifted off the ground and moved upwards, towards the surface, and Tony wanted to scream and cry and _breathe_ , fuck, he couldn't breathe –

His lungs felt like they were filled with tiny needles, every second absolute agony, and he'd just closed his eyes against the dark spots in his vision when he suddenly broke the surface, water cascading down inside the armor until –

Tony gasped in a desperate breath that burned all the way down into his lungs, coughing and choking on it as he bobbed in the water, held up by some invisible force. He jolted when something swished against his legs, his head whipping down to see nothing but black water. His whole body was shivering in the armor and when he looked over the coast was only a smattering of lights in the distance, too far for him to swim before he'd succumb to the cold.

The tears that ran down his cheeks burned hot on his chilled skin and Tony cursed, slapping the water with his gauntlets. This was hopeless; Tony was going to die out here and no one would even know.

He suddenly tasted sand in the back of his throat, almost choking on it as he took deep, rasping breaths, and it made him angry, so fucking furious that he screamed, ripping at his now useless gauntlets until they came off and he could throw them away.

They sunk quickly but Tony didn't care, going for his helmet next before he reached for the chest plate's emergency releases –

And touched skin.

He yelped, letting go with a jolt and immediately sank under the surface, ripping his eyes open in terror –

And a man looked back at him with wide eyes. Before Tony could react they narrowed in determination and the man grabbed him under his arms, pulling him back up.

Tony broke the surface with a gasp, his mind reeling as he reflexively reached down to grab the man's wrist, feeling muscles jump under his hands. The man kept his head under the water and Tony stared at the ocean, waiting for him to come up.

After at least five minutes in which the man's grip didn't falter Tony cleared his throat, reaching out blindly until he found the man's shoulder and tapped it.

“Uh... M-maybe you sh-should breathe?” His teeth were chattering enough to slur his words now. Fuck, he needed to get out of here. “Hello?”

When he didn't get an answer Tony reached for the man's wrists again, shifting them lower on his chest so he could get at the release catches. It took him a few tries with his trembling fingers but he finally got it open, letting the plate fall away from his shivering body. He immediately felt lighter, bringing his arms up to start swimming, but his limbs felt stiff and awkward, too numb to really work up any energy.

But he couldn't leave that man out here. Maybe he was a professional diver or something because it had been minutes and he'd still not come up for air.

“H-hel-lo?” Tony tried again, his lips feeling swollen and numb, but he didn't get an answer. The man's hands had disappeared and when Tony reached out with his feet he found nothing but water. Maybe he'd just imagined it. Fuck, he was cold.

He turned towards the city lights and started swimming, one stroke after the other until he didn't know if he was still moving or just floating like dead weight in the sea. The lights kept flickering in front of his eyes until they were nothing but a blurry mess, drenched in sea salt and dirty water that Tony was too cold to really feel the sting of. His arms were so, so heavy and Tony found it harder and harder to keep his head above the water that was starting to feel strangely warm, almost like an embrace as he closed his eyes.

 _Maybe I'll see Yinsen_ , was his last thought, bringing a smile to his face as he laid his head and slept.

Tony woke up warm.

He hummed, snuggling down into the embrace of strong arms, burying his toes in the sand. He must have fallen asleep at some point. Weird that no one had tried to wake him; he was pretty sure he had a charity thing today and –

_Sand?_

Tony sat up so fast it made him dizzy, hissing out a groan as he massaged his aching temples. His whole body felt sore and... salty? He grimaced as he looked down at the layer of – oh, fuck, he was naked. And had crusted salt all over him. The fuck?

Something moved behind him and Tony shrieked, whipping around at the man who startled back, scurrying across the sand on –

Tony blinked. No. That was – what?

Before he could react the man had made it into the water and Tony surged forward, grabbing his arm before he could completely disappear.

“Wait! What are you –“

The man's tail – his _fish tail_ – swished behind him just enough to show the scales glistening in the sun and Tony's mouth went dry, his mind reeling because that couldn't – that wasn't –

“You're a mermaid?” he asked in a high-pitched voice and the man looked away, his face hard and – afraid?

“Mer _man_ actually,” he said in a surprisingly pleasant voice that didn't hide the fact that he was still trying to pull away from Tony's grip. “Please let me –“

“You,” Tony breathed, a bunch of random memories from last night suddenly falling into place. “You saved me. That was _you_.”

The man squirmed but he stopped struggling against Tony, just looking kind of uncomfortable. “I... wasn't supposed to.”

 _Mermaids exist. And I'm talking to one_. Either Tony was going insane or he'd have to do an overhaul on his concepts of reality.

“Am I dead?” he asked and the man blinked before his brow furrowed in a concerned frown.

“You almost died. I didn't –“ He looked away, something almost like guilt on his face. “I thought you'd make it on your own.”

“Oh.” Tony mustered the man, getting stuck on the tiny dorsal fins of his fish tail. They were fluttering in the breeze and Tony was surprised to feel his heart start pounding. “You, uh. Are you okay out of the water?”

“What?” The man looked back at his tail and it splashed, just once, making Tony flinch. Holy shit, it was real, this man had a fucking tail, holy fuck – “I don't know. I've never – I mean...”

“You've never been out of the water?” Tony asked and the man grimaced. “Wow. So you... you live in the ocean?”

The man's head snapped up, his eyes suddenly filled with fear as he shook his head, shuffling backwards. “I don't – I shouldn't be here. I shouldn't –“

“Hey, it's okay,” Tony said but the man pulled out of his grip, twisting to throw himself into the water, and with a strong whip of his tail he was gone. Tony blinked, staring at the ripples in the sea until they disappeared and it was like the man had never been there. He rubbed a hand across his face with a tired chuckle. “Fuck. I'm fucking losing it.”

Tony tried to get up but almost immediately fell flat on his ass, groaning at the stab of pain in his... well, everything. It took a lot of effort to get himself upright and by the time he'd made it into a crouch and got a good look at his surroundings –

“You've got to be _kidding_ me,” he groaned, turning around just to be sure – but yeah, this wasn't the mainland. He was on some tiny cluster of rocks somewhere in the middle of bumfuck nowhere and the shore was only visible if he squinted. Fan-fucking-tastic.

Tony sighed, about to put his head in his hands when he noticed a wash of blonde hair peeking over a rock to his right. As soon as he looked over it disappeared and Tony heard a splash as the man dove underwater again.

"You can come out, you know?” he shouted. “I don't bite."

There was no answer but Tony hadn't really expected one. He shrugged, standing up and looking around for the clothes he'd been wearing under his suit. Sure enough they were lying in a pile a little ways off and Tony sighed as he picked them up, patting the sand off them before he started wringing them out. He'd survived worse than swimming a couple miles home in wet clothes but that didn't mean he was looking forward to it.

"You're different than I expected."

Tony whipped around, his sudden movement startling the man back under the surface until only his eyes were peeking out, studying him warily.

"Shit. I'm sorry,” Tony said, raising his hands placatingly. “You scared me. I'm not going to hurt you."

The man still looked skeptical so Tony stayed right where he was, giving him a smile.

"I'm Tony by the way. Forgot to say that earlier. What's your name?"

The man hesitated before he made a loud chittering sound. Tony cocked his head and the man smiled, coming closer to shore until he could prop himself up on the sand, his lower half still submerged in the water.

"My friends and I, we used to give each other human names when we were children."

"Different ones?" The man nodded. "What was your favorite?"

"Steve," the man said immediately and Tony smiled.

"Steve it is then. Hi, Steve."

"Hi, Tony," Steve said, looking honestly delighted, and Tony had to stop and stare at him for a moment. He was seriously beautiful.

"So, Steve." Tony ventured forward slowly and - when Steve didn't move away - sat down next to him in the sand. "You think you could get me back to main land? I'm kind of stuck here."

"Oh." Steve looked at the coast, then back to Tony. "You want to go there?"

"Yes, very much." Steve hesitated, so Tony put a hand on his arm, quietly thrilled that he was touching a _merman_ , holy fuck – "You don't have to take me all the way. But I can't swim that far on my own."

Steve stared at his hand for a long moment before he nodded. "Okay," he said, looking up at Tony almost a little wistfully. "Now?"

"Sure. Let me just get my things."

Tony grabbed his clothes, considered putting them on and then tied them into a big knot that he could sling around his shoulders like a backpack. No point putting them on if he'd just have to wring them out again.

When he turned around he froze, staring at Steve who's eyes were firmly fixed on Tony's – well, his cock. Tony barely resisted the urge to cover himself. "Um. You okay?"

Steve snapped out of it, barely meeting Tony's eyes before he turned away, his neck and ears bright red. "Yes!"

Tony just stood there, needing a moment to process that a merman had just checked him out and apparently liked what he saw. He took a deep breath, forcibly clamping down on the thought that Steve was really hot and to his knowledge no one had ever had sex with a merman and –

No. Steve had saved his life and Tony would be grateful for that. Nothing more.

"Okay, I'm ready," Tony said and Steve nodded, giving him a slightly tense smile.

"I'll take you halfway," he said as Tony walked gingerly into the water, hissing at the cold. At least it wasn't as bad as last night. "Then you can swim the rest."

"Sounds good," Tony said, wading in until he was submerged up to his nipples, shivering a little. "Damn, that's cold."

"Are you okay?" Steve asked with a concerned crease in his brow and Tony waved him off.

"Nothing I can't handle. Now how do we -" He broke off, abruptly realizing that by not putting on his clothes he was doomed to cling to Steve naked now, holy shit, why hadn't he thought of that?

"You could hold on to me?" Steve sounded a little unsure so Tony waded towards him and grabbed Steve's shoulders from behind. Steve's tail was so close now, glimmering red and blue under the surface and Tony sucked in a breath when the fin brushed against his bare legs, feeling Steve shudder against him.

"That could work," Tony said hoarsely, patting Steve's shoulders. "You could – whoa!"

He reeled back when Steve's whole body jerked, spinning in Tony's arms until they were facing each other and Steve could catch his wrists in a tight grip. His pupils were blown so wide they looked black, his breathing suddenly hard and fast.

"What are you doing?" Steve panted and Tony froze, thinking back to the last few seconds. He hadn't done anything, had he?

"I – what?"

"Do you want to –" Steve swallowed heavily, suddenly looking excited. "You want to mate?"

Tony's brain screeched to a halt. "What? No, I – What gave you that idea?"

Steve's smile dropped, his brow furrowing into a disappointed frown. "But you –" He gestured at his shoulders and Tony shook his head, confused.

"I'm not following."

"You signaled me," Steve said, sounding almost accusing now, and Tony twisted his wrists out of Steve's grip so he could hold up his hands.

"Okay, I think there's a misunderstanding here. On my part, probably. What do you mean by signal?" Steve looked perplexed by his ignorance, so Tony shrugged helplessly. "We don't have that where I'm from. Or – I mean, I guess we do, but it works differently. What did I do?"

"Oh." Steve's eyes lit up with understanding, then embarrassment as he sank a little deeper into the ocean. "You, uh. You flapped me? With your hands, here."

He pointed at his shoulders and Tony felt his mouth form an 'O' as he finally got it.

"Oh, that? Sorry, I didn't know that – I mean, it's a gesture of... I don't know, gratitude? Comfort? Something like that."

Steve nodded, his face going red. "Oh. I'm sorry, I... misunderstood."

"No problem." Tony really shouldn't ask but – "So, that flapping thing. Is that a come on? An invitation?"

Steve made a small noise, his blush darkening. "It's, uh. Very direct. It means you're getting me ready to mate."

"Getting you ready?" Tony frowned in confusion. "How does that –" He broke off when he suddenly realized something. "Wait, you thought I wanted to have sex with you and you... would have let me?"

Steve glanced at him from the corner of his eye. "Yes."

Holy shit.

"Why?" Tony asked, honestly baffled, and Steve gave him an incredulous look, his tail swishing next to Tony's feet.

"Why? I've never – You're probably the only human I'll ever meet and you –" Steve paused, biting his lip before he continued. "You're beautiful."

Oh. Okay.

"I see," Tony said slowly, watching as Steve's face fell a little. He reached out to grab Steve's shoulder again, waiting for Steve to meet his eyes before he very deliberately raised his hand and patted it. Steve jerked, his eyes going wide even as they filled with joy. Tony cleared his throat. "Do you – uh. Wanna try this again? Cause to be honest it's unfair how gorgeous you are and I really want to –"

"Yes!" Steve practically shouted before he was suddenly right in Tony's face and – dove underwater? Tony turned to see where he went when Steve suddenly resurfaced at his side, gripping his neck before he abruptly started humping him.

...No, not humping him.

“Um...” Tony blinked and Steve seemed to realize how confused he was because he stopped smacking his tail against Tony's side, already breathing hard.

“What's wrong? Don't you want –“ He bit his lip and Tony shook his head, reaching out to grab Steve's shoulder.

“No, I do, it's just – what are you doing?”

Steve looked at him for a long moment before he exhaled heavily through his nose, lowering his head. “That's not how humans mate, is it?”

“No.” Tony tightened his grip when Steve pulled back, a defeated slump to his shoulders. “Wait, we can figure this out. Did that – That did something for you, right?”

Steve nodded hesitantly. “Yes, we... It's to coax it out. The –“ He gestured at his lower half. “You know.”

“Your dick?” Tony asked and Steve stared at him blankly, so Tony reached down to grab his own. “Male sex organ. You do have one, right?”

“ _That's_ –?“ Steve's eyes widened as he stared down into the water before he dove underneath the surface, presumably to check out Tony's cock. Tony held still until Steve came up again, his brow furrowed. “No. I don't have that.”

“Oh.” Tony reached out cautiously, grabbing Steve's hip and slowly sliding his hand down until his fingers brushed the place where his skin melted into scales. Steve's breathing hitched and Tony looked up at him, swallowing when he saw how dark Steve's eyes were. “So how do you have sex? Do you have... I mean, how do you penetrate?”

“Penetrate?” Steve echoed, like the word didn't make sense. “Penetrate what?”

“The –“ Tony grasped for words. “I mean, your partner, I guess.”

Steve's brow furrowed. “We're still talking about mating, right?”

“Yes, of course.” When no answer seemed to be forthcoming Tony sighed, gripping the bridge of his nose. “Okay, just – explain to me how you have sex. Like I'm four years old and really, really dumb.”

“I wouldn't tell a four year old about sex,” Steve said, grinning when Tony gave him an unimpressed look. “Okay, so, uh...” He looked out at the ocean for a moment. “Some of us lay eggs and some of us have sperm. They're hidden in a – How do I say that?” He frowned, chittering something in mer-speak. “Like a – uh. Canal? On the inside?”

“Okay, makes sense.” Tony nodded. “Go on.”

“So when –“ Steve flushed, his tail swishing under the water. “When we need to mate, we massage the canal from the outside so that – so the eggs come out. And then the sperm to cover them.”

“Oh.” External fertilization. Tony remembered reading about that at some point. “That's what you meant by flapping, right?” Steve nodded and Tony hummed, tapping his fingers on Steve's shoulder. “So you're stimulated by... slapping against your sides?”

“Yes,” Steve said and Tony experimentally reached down to pat Steve's flanks. He couldn't build up much of a momentum underwater but Steve still gasped for it, jerking in Tony's grip. It was pretty damn hot.

“Are there other kinds of touching? Or just this?”

Steve shook his head, his eyes closing when Tony kept going. His tail was starting to get in on the action too, whipping through the water in tiny jerks.

“No, we – Touching isn't... we don't do that a lot.”

“What, in general?” Tony asked, thinking back to how Steve had reacted every time Tony touched him. “Actually, that explains a lot.”

“It's –“ Steve gasped, arching into Tony's hands when they slid even further down, patting over his scales. “Feels like... a lot.”

“So the flapping is just for your partner? Or...” He trailed off when Steve shook his head.

“No. It feels good to – I mean, it's hard not to when you're –“

“Horny?” Tony guessed and Steve flushed.

“Yeah.”

“Okay.” Tony was already wracking his brain for how best to do this when Steve suddenly tapped his cheek, pulling him back to reality. “What?”

“I asked how _you_ do it. Humans,” Steve said with an amused tilt to his lips and Tony was struck with the sudden urge to kiss him. He shook his head to snap out of it.

“Right. Well, humans have eggs and sperm too, we just fertilize them on the inside instead of outside.”

“Inside?” Steve asked confusedly and Tony gestured at his dick.

“That's why it's... sticking out. So I can put it in someone else's body.”

“Oh.” Steve looked down at himself, a forlorn little furrow in his brow. “I don't –“

“It doesn't have to be inside anything to work,” Tony reassured him quickly. “We just... If you mimic the sensation of it then you're golden.” He mimed jerking off with his hand above the water. “Just heat and friction, that's all it is.”

“Okay.” Steve glanced between their bodies. “So how do we –“

“Well...” Tony shrugged. “Technically, if you do your flapping thing against my front, where my cock is, it should work for both of us, right?”

Steve pondered this for a moment before he nodded. “Yes. That could work.”

“Fantastic. Let's do it.”

They moved around until Tony was standing at Steve's side, his legs slightly spread so his cock was pressed into Steve's hip. He'd gone completely soft during their talk, but feeling the surprisingly squishy texture of Steve's scales on him... fuck yeah, he could get behind that.

Or beside that. Technicalities.

“Ready?” Steve asked, sounding a little nervous and a lot excited, and Tony nodded. He winced at the first slap of Steve's tail on his crotch, grimacing when the pressure didn't let up, too strong to really be enjoyable. Steve seemed to notice his predicament because he stopped after only a few seconds, his cheeks a little flushed. “What's wrong?”

Tony grabbed his cock, giving it a few jerks to get it back in the mood after that ordeal. “Could you – flap a little less maybe?“

“Less?” Steve asked incredulously and Tony nodded, wrapping an arm around Steve's neck.

“We're usually more... you know. We make smaller movements.”

“Oh.” Steve stopped, looking at Tony's dick consideringly. “So how do I...”

“I'm sure if you – yeah,” Tony groaned when Steve's tail pressed up against his cock again. “Fuck. That's good, perfect. Now if you just hold still I can –“

He jolted, his fingers tightening their grip on Steve as he gasped, and Steve froze, looking at him with wide eyes.

“Was that –“

“Good, that was good, holy shit –“ Tony panted and Steve smiled, fitting them together and fluttering his tail again. It almost felt like a vibrator, but so much better, his slick scales a completely foreign texture on Tony's cock. “Oh fuck, that's _really_ good.”

“I'm glad it's good,” Steve said quietly, like his vibrating didn't cause him any effort at all, and Tony wrapped his legs around his tail to pull him closer. He looked up when Steve sucked in a breath.

“What?”

Steve's eyes were dark when he looked down, cautiously reaching out to touch Tony's bare legs. Tony felt it when a shiver ran down Steve's spine, his whole body shaking.

“Oh wow,” Steve breathed and Tony crossed his ankles, squeezing down with his thighs. The pressure made Steve gasp, his fingers spasming on Tony's skin.

“You like my legs?” Tony guessed and Steve nodded, his cheeks flushed. “Hey, no shame in it. I do have some nice quads.”

“Quads?”

“Never mind.” Tony squeezed him again and Steve jolted, his eyes rolling into the back of his head.

“Oooh –“

“Is that good?” He asked, rhythmically tensing and releasing his muscles as he started thrusting against Steve, his mouth dropping open when Steve's vibrations picked up. “Oh, shit –“

“More –“ Steve ground out and Tony reached down to push his hands into Steve's sides and drag them down. He had no idea where Steve's 'canal' was or if this was doing the job of massaging it, but Steve suddenly let out a trilling whistle, so high-pitched it couldn't have been made by his human vocal cords, as he – oh shit.

Tony barely managed to take a deep breath before Steve suddenly dove, taking Tony under the surface with him as his body curled, his tail wrapping around Tony. It took a few seconds before he seemed to realize his mistake, his eyes snapping open in panic before he brought them back up so Tony could gasp for air.

“Oh my god, Tony, I'm so sorry, I –“ Tony cut off his babbling with a hand over his mouth until he caught his breath. Steve looked like a deer in the headlights, his eyes filled with guilt, and Tony couldn't resist leaning forward and pressing a kiss to his lips, only noticing after the fact that they hadn't done this yet. He pulled away and Steve gave him a bewildered look, suddenly stiff as a board.

“Why did you do that?”

Tony chuckled. “I'm gonna take a wild guess and say that merpeople don't kiss?”

“Kiss?” The way he said it was answer enough. “No, we don't. What does it do?”

“It just feels good.” Steve looked a little skeptical so Tony pulled him closer to fit their lower halves together. “We don't have to do it. But if you wanna try that flapping thing again, I'd love to –“

“No, I want to.” Steve grabbed Tony's face, bringing him close enough that they shared the same air. “Show me, please.”

Fuck. That shouldn't be as hot as it was.

“Alright. Just copy what I'm doing.” Tony leaned in slowly, telegraphing his movements clearly as he pressed his lips to Steve's just enough that they dragged softly against each other before he pulled away again. He did it over and over until Steve got the hint and moved with him, opening his mouth a little to make the glide even better. Tony hummed and felt the way Steve shivered at the sound before he pulled away, gauging Steve's reaction.

“Okay?” he asked and Steve nodded eagerly, leaning in to kiss Tony with a little more force. Tony met him halfway, opening his mouth a bit more on each pass until he could taste Steve, bringing his tongue into the mix. At Tony's first attempt to push it into Steve's mouth however Steve pulled away, wrinkling his nose.

“That feels weird.“

“Okay, no tongue, got it.” He could feel Steve's tail swishing between his legs as they kissed again, so he reeled it in with his ankles, fitting it properly on his crotch. It was a relief to thrust against him, his cock so hard it was starting to ache, and Steve seemed to agree, his whole body trembling as he started to flap again.

Steve made a muffled moan against Tony's mouth when Tony reached down to grab his sides and squeezed them as hard as he could, massaging downwards. His vibrating picked up speed until it was just on the right side of rough and Tony's hips hitched forward all on their own, rubbing up against Steve's quivering scales.

“Oh, fuck –“ he groaned and Steve swallowed it hungrily, their lips sliding together all soft and wet and oh fuck, Tony could already feel it building in his gut, his cock throbbing with it –

“Ah!” Steve gasped, his moans turning more and more high-pitched until he trilled again, burying his face in Tony's neck as his flapping turned frantic, his whole body jolting until – “Ooooh...”

The sudden rush of warmth in the water made Tony's head spin, feeling it slosh all around his crotch, his thighs, his _balls_ , fuck –

Tony grabbed Steve's tail in both hands as he thrust against it desperately, chasing his orgasm as Steve kept jerking between his legs, his fins fluttering. “Ste– _eve!”_

“Okay?” Steve panted and Tony nodded frantically, eyes squeezing shut against the pleasure when Steve started vibrating again, fuck, it was so good, he couldn't –

It hit him like a punch in the gut, like someone had reached through his cock to drag his orgasm right out of him. He came for what felt like ages before the tension left him all at once and he would've sunk like a stone if not for Steve's strong arms holding him up. His breathing was all over the place but to his surprise Steve seemed barely affected, his whole demeanor calm and steady.

“Holy fuck, that was so good,” Tony panted and Steve chuckled, letting go of him as soon as Tony could hold his own weight again, his eyes twinkling with joy.

“Yeah, it was.” Steve nodded at the open water. “You still want to get to shore?”

Tony stared at him, a little thrown by the sudden change in subject, but then nodded cautiously. “Yeah. I'd like that.”

“Okay.” Steve turned his back on him, sinking further into the water. “Climb on. I'll take you there.”

“Gimme a minute, Jesus,” Tony said with a small laugh, putting a hand over his still racing heart. “I'm fucking wiped. I don't think I have much grip strength right now.”

Steve looked at him with a confused furrow in his brow. “What? Why?”

“Cause I just came?” He smiled when Steve just cocked his head. “I guess orgasm doesn't tire you out?”

“No,” Steve said, almost a little indignant. “That would be – no.” He finally seemed to notice Tony's state of general exhaustion, his face softening with understanding. “Oh. It... makes you tried?”

“Yep,” Tony said, popping the 'p'.

“That sounds... inconvenient.” Steve looked genuinely put out and Tony couldn't help but laugh at his expression, shaking his head.

“Yeah, I don't know. I guess evolution figured out that as an apex predator we're not in danger when we fuck. Don't have to bail immediately after.”

“Huh.” Steve looked like he was considering that. “Still.”

“Yeah, I mean. It _can_ be annoying sometimes.” Tony shrugged. “At least you know when your partner enjoyed themselves.”

“Oh.” The small smile that bloomed on Steve's face at that was unfairly beautiful. “You enjoyed it?”

“Course I did.”

Steve's tail flicked in the water until the fins brushed Tony's legs, wrapping around his ankles. “Yeah?”

“Yeah.” Steve looked very pleased with that and Tony couldn't resist pressing a kiss to the proud tilt of his smile. “Now take me home, romeo.”

“Romeo?”

“Not important.” Tony grabbed onto Steve's shoulders, unsure whether he should straddle him or not. In the end he wrapped his legs around Steve's waist and clung to him like a koala, delighting in the way Steve touched his legs gently, something like awe written on his face.

“They're so...” Steve couldn't seem to find the words so he shook his head, grabbed Tony's arms to wrap them more securely around his shoulders and took off, his tail whipping through the water at a speed that made Tony's head reel, his eyes squeezed tightly shut against the splashing water.

They made it to the shore in no time at all, stopping a quarter mile out so Tony could swim the rest on his own. Steve let him go cautiously, like he thought Tony would drown the second he let go, and Tony rolled his eyes.

“I can swim, you know? When I'm not encased in half a ton of metal, that is.”

“Yeah, I know,” Steve said and there was something forlorn in his gaze when he looked at Tony. “I don't think I'll ever see you again.”

His words hit Tony hard. They had barely known each other a day, but even so Tony felt his heart sink at the thought of Steve disappearing from his life just like that.

“Never say never,” he said jokingly but it was half-hearted at best and Steve seemed to know it, his lips quirking into a sad smile.

“I'll remember you always.”

Tony swallowed hard around the lump in his throat. “Yeah. Ditto.”

Steve gave him one last look before he pushed off, the movement of his tail making it brush against Tony's chest one last time before he bent backwards and dove, disappearing into the ocean depths. Tony stared after him until a sudden wave splashed water in his face, making him wipe salt out of his eyes before he started towards the shore. A few times he thought he caught a flash of red and blue just under the surface but when he turned to look there was nothing there. Still, the thought that Steve was escorting him to the shore was a nice one, even if it made his heart twist.

When he'd finally climbed onto mainland and struggled into his wet clothes he couldn't resist one last look out at the ocean, imagining that Steve was out there watching as he left and hailed down a taxi. He made it to the tower in one piece, ignoring all the weird looks he got walking through the building completely drenched, until the door to his workshop finally closed behind him and he could take a deep breath.

“Good morning, Sir. I have to say I am very glad to see you.”

Despite his heavy heart Tony felt his lips twist into a smile. “Yeah, you too, J.”

“The test flight took a sudden dive, I take it?”

Tony snorted, taking his shirt off and handing it to DUM-E who immediately started wringing it out into a bucket. “You could say that, yeah.”

“That is unfortunate. Might I suggest you take a warm shower? You might catch a cold.”

“Later.” Tony leaned on the table as he brought up his armor schematics. “Say, JARVIS. How long do you think it would take to make the armor waterproof? As in deep sea compatible. A diving mode.”

“The speed would depend on your determination, Sir, as always,” JARVIS said. “May I inquire as to your sudden interest?”

“No reason,” Tony said absently, twirling a screwdriver between his fingers as he thought back to the reflection of the morning sun in Steve's eyes. “No reason at all.”

**Author's Note:**

> A bit of trivia for you lovely people:
> 
> \- There are many different ways for fish to procreate, some of them internal and some of them external  
> \- Tony says that humans are 'apex predators' in this fic, meaning they are the top of their food chain with no natural enemies, but that is a largely controversial definition. Some people say we are apex predators, some say we aren't. So take it with a grain of salt  
> \- Also, if you were confused as to the mechanics of the 'flapping' in this fic, [watch this](https://www.youtube.com/watch?v=9V-9eOppBkg). Warning, graphic (and funny) fish content ahead


End file.
